Deploying Gateway using a Raspberry Pi, DNS over HTTPS and Pi-hole

Like many who are able, I am working remotely and in this post, I describe some of the ways to deploy Cloudflare Gateway directly from your home. Gateway’s DNS filtering protects networks from malware, phishing, ransomware and other security threats. It’s not only for corporate environments - it can be deployed on your browser or laptop to protect your computer or your home WiFi. Below you will learn how to deploy Gateway, including, but not limited to, DNS over HTTPS (DoH) using a Raspberry Pi, Pi-hole and DNSCrypt.

We recently launched Cloudflare Gateway and shortly thereafter, offered it for free until at least September to any company in need. Cloudflare leadership asked the global Solutions Engineering (SE) team, amongst others, to assist with the incoming onboarding calls. As an SE at Cloudflare, our role is to learn new products, such as Gateway, to educate, and to ensure the success of our prospects and customers. We talk to our customers daily, understand the challenges they face and consult on best practices. We were ready to help!

One way we stay on top of all the services that Cloudflare provides, is by using them ourselves. In this blog, I'll talk about my experience setting up Cloudflare Gateway.

Gateway sits between your users, device or network and the public Internet. Once you setup Cloudflare Gateway, the service will inspect and manage all Internet-bound DNS queries. In simple terms, you point your recursive DNS to Cloudflare and we enforce policies you create, such as activating SafeSearch, an automated filter for adult and offensive content that's built into popular search engines like Google, Bing, DuckDuckGo, Yandex and others.

There are various methods and locations DNS filtering can be enabled, whether it’s on your entire laptop, each of your individual browsers and devices or your entire home network. With DNS filtering front of mind, including DoH, I explored each model. The model you choose ultimately depends on your objective.

Butfirst, let’s review what DNS and DNS over HTTPS are.

DNS is the protocol used to resolve hostnames (like www.cloudflare.com) into IP addresses so computers can talk to each other. DNS is an unencrypted clear text protocol, meaning that any eavesdropper or machine between the client and DNS server can see the contents of the DNS request. DNS over HTTPS adds security to DNS and encrypt DNS queries using HTTPS (the protocol we use to encrypt the web).

Let’s get started

Conceptually similar to HTTPS traffic, when our edge receives an HTTPS request, we match the incoming SNI header to the correct domain’s configuration (or for plain text HTTP the Host header). And when our edge receives a DNS query, we need a similar mapping to identify the correct configuration. We attempt to match configurations, in this order:

DNS over HTTPS check and lookup based on unique hostname

IPv4 check and lookup based on source IPv4 address

Lookup based on IPv6 destination address

Let’s discuss each option.

DNS over HTTPS

The first attempt to match DNS requests to a location is pointing your traffic to a unique DNS over HTTPS hostname. After you configure your first location, you are given a unique destination IPv6 address and a unique DoH endpoint as shown below. Take note of the hostname as you will need it shortly. I’ll first discuss deploying Gateway in a browser and then to your entire network.

DNS over HTTPS is my favorite method for deploying Gateway and securing DNS queries at the same time. Enabling DoH prevents anyone but the DNS server of your choosing from seeing your DNS queries.

Enabling DNS over HTTPS in browsers

By enabling it in a browser, only queries issued in that browser are affected. It’s available in most browsers and there are quite a few tutorials online to show you how to turn it on.

Chromium based browsers

Using Chrome as an example on behalf of all the Chromium-based browsers, enabling DNS over HTTPS is straightforward, but as you can see in the table above, there is one issue: Chrome does not currently support custom servers. So while it is great that a user can protect their DNS queries, they cannot choose the provider, including Gateway.

Here is how to enable DoH in Chromium based browsers:

Navigate to chrome://flags and toggle the beta flag to enabled.

Firefox

Firefox is the exception to the rule because they support both DNS over HTTPS and the ability to define a custom server. Mozilla provides detailed instructions about how to get started.

Optionally, you can enable Encrypted SNI (ESNI), which is an IETF draft for encrypting the SNI headers, by toggling the ‘network.security.esni.enabled’ preference in about:config to ‘true’. Read more about how Cloudflare is one of the few providers that supports ESNI by default.

Congratulations, you’ve configured Gateway using DNS over HTTPS! Keep in mind that only queries issued from the configured browser will be secured. Any other device connected to your network such as your mobile devices, gaming platforms, or smart TVs will still use your network's default DNS server, likely assigned by your ISP.

Configuring Gateway for your entire home or business network

Deploying Gateway at the router level allows you to secure every device on your network without needing to configure each one individually.

Requirements include:

Access to your router's administrative portal

A router that supports DHCP forwarding

Raspberry Pi with WiFi or Ethernet connectivity

There aren't any consumer routers on the market that natively support DoH custom servers and likely few that natively support DoH at all. A newer router I purchased, the Netgear R7800, does not support either, but it is one of the most popular routers for flashing dd-wrt or open-wrt, which both support DoH. Unfortunately, neither of these popular firmwares support custom servers.

While it’s rare to find a router that supports DoH out of the box, DoH with custom servers, or has potential to be flashed, it’s common for a router to support DHCP forwarding (dd-wrt and open-wrt both support DHCP forwarding). So, I installed Pi-hole on my Raspberry Pi and used it as my home network’s DNS and DHCP server.

Getting started with Pi-hole and dnscrypt-proxy

If your Raspberry Pi is new and hasn’t been configured yet, follow their guide to get started. (Note: by default, ssh is disabled, so you will need a keyboard and/or mouse to access your box in your terminal.)

Once your Raspberry Pi has been initialized, assign it a static IP address in the same network as your router. I hardcoded my router's LAN address to 192.168.1.2

Configuring DNS and DHCP in the Pi-hole administrative console

Go to Settings -> DNS to modify the upstream DNS provider, which we’ve just configured to be dnscrypt-proxy.

Change the upstream server to 127.0.0.1#5054 and hit save. According to Pi-hole's forward destination determination algorithm, the fastest upstream DNS server is chosen. Therefore, if you want to deploy redundancy, it has to be done in the DNSCrypt configuration.

Almost done!

In Settings->DHCP, enable the DHCP server:

Hit save.

At this point, your Pi-hole server is running in isolation and we need to deploy it to your network. The simplest way to ensure your Pi-hole is being used exclusively by every device is to use your Pi-hole as both a DNS server and a DHCP server. I’ve found that routers behave oddly if you outsource DNS but not DHCP, so I outsource both.

After I enabled the DHCP server on the Pi-hole, I set the router’s configuration to DHCP forwarding and defined the Pi-hole static address:

After applying the routers configuration, I confirmed it was working properly by forgetting the network in my network settings and re-joining. This results in a new IPv4 address (from our new DHCP server) and if all goes well, a new DNS server (the IP of Pi-hole).

Done!

Now that our entire network is using Gateway, we can configure Gateway Policies to secure our DNS queries!

IPv4 check and lookup based on source IPv4 address

For this method to work properly, Gateway requires that your network has a static IPv4 address. If your IP address does not change, then this is the quickest solution (but still does not prevent third-parties from seeing what domains you are going to). However, if you are configuring Gateway in your home, like I am, and you don’t explicitly pay for this service, then most likely you have a dynamic IP address. These addresses will always change when your router restarts, intentionally or not.

Lookup based on IPv6 destination address

Another option for matching requests in Gateway is to configure your DNS server to point to a unique IPv6 address provided to you by Cloudflare. Any DNS query pointed to this address will be matched properly on our edge.

This might be a good option if you want to use Cloudflare Gateway on your entire laptop by setting your local DNS resolution to this address. However, if your home router or ISP does not support IPv6, DNS resolution won’t work.

Conclusion

In this blog post, we've discussed the various ways Gateway can be deployed and how encrypted DNS is one of the next big Internet privacy improvements. Deploying Gateway can be done on a per device basis, on your router or even with a Raspberry Pi.